Question

$Si$ can form more than $4$ bonds but $B$ can not because :

• A. $Si$ has empty d-orbitals
• B. $Si$ has empty p-orbital
• C. Size of $Si$ is considerable
• D. It has more than $4$ valence electron

Answer 1

Answer: (A), (C)

Size of $Si$ is considerable
$Si$ has empty d-orbitals

A boron atom only has 3 electrons in its outer level, and there is no possibility of it reaching a noble gas structure by simple sharing of electrons. Hence, Boron donates the lone pair of electrons to form the fourth bond. In addition to that Boron is a second period element hence, which makes it small in size and d-orbitals are unavailable as well. Hence, Boron cannot form more than 4 bonds.

On the other hand, Silicon has 6 valence electrons in outer shell. It is a 3rd period element hence, it's size is considerable and also has vacant d-orbitals.